Blood pressure (BP) is a critical vital sign for health, including hypertension. Clinical practice, however, is largely limited to awkward, inconvenient arm cuffs that provide only point-in-time measurement. High- throughput screening as well as personal health monitoring would benefit from a simple BP monitor that obtains accurate measurements with no training-ideally in seconds rather than minutes-and includes electronic health record (EHR) integration to minimize patient reporting error and noncompliance. The overall objective of this project is to use ultrasound, and in particular, Acoustic Radiation Force Impulse (ARFI) techniques, to develop an easy-to-use, cuffless, noninvasive, ultrasonic BP monitor, consisting of a compact sensor pad and readout. Placement of the pad in contact with the skin over an artery will immediately provide self-calibrated, accurate BP. The operating principle is analogous to a conventional arm cuff, which relies on acoustically observing arterial wall deflection in response to the differential between internal arterial pressure and an externally applied cuff pressure; however, this project will instead use ultrasound energy to impose highly localized but safe ARFI pressure pulses on an arterial wall and measure the microscopic deflection that results from the pressure differential. Furthermore, the high speed of ultrasound will allow blood pressure to be conveniently assessed in just a few seconds. The first Aim will demonstrate the ultrasonic pressure measurement method, on a commercial ultrasound testbed, by: developing algorithms to noninvasively track the pulsatile waveform using measured displacements in response to ARFI pulses; calibrating the pressure strength of the ARFI pulses; and reporting the absolute systolic and diastolic equivalent pressures for fluid- and blood-filled arterial phantoms, finishing with human clinical evaluation o the method according to the IEEE 1708-2014 Standard for cuffless blood pressure devices. The second Aim will seek to replace the piezoelectric testbed transducer with a low-cost capacitive micromachined ultrasonic transducer (which is well-suited to affordable personal health monitoring applications), likewise ending with clinical evaluation according to the IEEE standard. The final Aim will translate the testbed into a prototype instrument with a specifically-designed readout unit, incorporate an EHR interface, and culminate with a clinical study to evaluate the complete health monitor system in a low-resource context. This project is particularly relevant to the Department of Health & Human Services' Million Hearts' Initiative, potentially touching a number of facets in the Million Hearts Logic Model by: improving measurement and reporting for large-scale epidemiological studies; increasing management effectiveness for ongoing hypertension medication; reducing hassle and barriers to use; and supporting further ambulatory research, both in the US and India.